From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751096AbaLOF5x (ORCPT <rfc822;w@1wt.eu>);
	Mon, 15 Dec 2014 00:57:53 -0500
Received: from mx1.redhat.com ([209.132.183.28]:52443 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1750736AbaLOF5v (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 15 Dec 2014 00:57:51 -0500
Date: Mon, 15 Dec 2014 00:57:07 -0500
From: Dave Jones <davej@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chris Mason <clm@fb.com>, Mike Galbraith <umgwanakikbuti@gmail.com>,
        Ingo Molnar <mingo@kernel.org>, Peter Zijlstra <peterz@infradead.org>,
        =?iso-8859-1?Q?D=E2niel?= Fraga <fragabr@gmail.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Suresh Siddha <sbsiddha@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
        Peter Anvin <hpa@linux.intel.com>
Subject: Re: frequent lockups in 3.18rc4
Message-ID: <20141215055707.GA26225@redhat.com>
Mail-Followup-To: Dave Jones <davej@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Chris Mason <clm@fb.com>, Mike Galbraith <umgwanakikbuti@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	=?iso-8859-1?Q?D=E2niel?= Fraga <fragabr@gmail.com>,
	Sasha Levin <sasha.levin@oracle.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Suresh Siddha <sbsiddha@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
	Peter Anvin <hpa@linux.intel.com>
References: <20141211145408.GB16800@redhat.com>
 <CA+55aFy1_w1NrkeopMXsxGftO5F03JzKgn-8uTQRnEAXuoiXgg@mail.gmail.com>
 <20141212185454.GB4716@redhat.com>
 <CA+55aFw7vJkuJ9RtVS3yhPsqDos+ii1kdJBZEeoxhb9c2=rStQ@mail.gmail.com>
 <20141213165915.GA12756@redhat.com>
 <20141213223616.GA22559@redhat.com>
 <CA+55aFwCa1+cBGxt-v487K-QBvxGyB9bL4u34zgMep9uFW+Mgw@mail.gmail.com>
 <20141214234654.GA396@redhat.com>
 <CA+55aFyUtZobUADgtss7e4w-yriMtz7hKVKs=Ed72KQoQ9n2nA@mail.gmail.com>
 <CA+55aFwE3gY+ChZtBpPtt_eY9nCj6pgF_wd8utRN9cOgRe2xOQ@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CA+55aFwE3gY+ChZtBpPtt_eY9nCj6pgF_wd8utRN9cOgRe2xOQ@mail.gmail.com>
User-Agent: Mutt/1.5.23 (2014-03-12)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, Dec 14, 2014 at 09:47:26PM -0800, Linus Torvalds wrote:

 > so it's always in __do_page_fault, but at sometimes it has gotten into
 > handle_mm_fault too. So it really really looks like it is taking an
 > endless stream of page faults on that "xsaveq" instruction. Presumably
 > the page faulting never actually makes any progress, even though it
 > *thinks* the page tables are fine.
 > 
 > DaveJ - you've seen that "endless page faults" behavior before. You
 > had a few traces that showed it. That was in that whole "pipe/page
 > fault oddness." email thread, where you would get endless faults in
 > copy_page_to_iter() with an error_code=0x2.
 > 
 > That was the one where I chased it down to "page table entry must be
 > marked with _PAGE_PROTNONE", but VM_WRITE in the vma, because your
 > machine was alive enough that you got traces out of the endless loop.

We had a flashback to that old bug last month too.
See this mail & your followup. : https://lkml.org/lkml/2014/11/25/1171
That was during a bisect though, so may have been something
entirely different, but it is a spooky coincidence.

	Dave